4spd conversion. What are the advantages?

[duneFJ40]

I have an opportunity to buy a 78 (4spd) transfer case and transmission for $350. The rig was running. He is selling the engine and trans (with case) for $600. I am somewhat local (3 hours away).

First, it that a good deal?
Second, What real advantages are there with a 4spd? My rig is a pretty stock 72 with 98,000 miles (3spd). Do I have to change the length of my drive shafts?

Thanks!

 

[Leaping Deer]

Advantages would be a lower first gear. Easier starting off.

Price for the tranny and t-case seems high assuming that its an H42. I paid $100 for a 4speed and t-case.

 

[Bgpig]

Just did mine

I have a 72 I just changed out for the 4 spd. In my opinion, it is worth it. Gives it a bit more top end when driving down the road. I especially like being able to shift into first gear when moving with the 4 speed.

I had to modify my drivelines. I had my rear shortened and the front lengthened. Local driveline shop did it for $195.00. I used my existing drivelines so I had to pull the rear parking brake hub and attach it to the 4spd. so the rear driveline would attach to it. For the front, I had to buy a different flange. I had to pull the one on the 4 speed off and mount the new flange to the transfer case so the front driveline flange would mount to the transfer case. I also had to modify my transmission hump openings and buy new boots for the both shifters.

As far as price, I don't know, my philosophy is to buy High and sell Low.

If you did this I would recommend you use a cherry picker to support the transmission when you take it out. Using a floor jack and 5 pieces of 2 X 6 is kind of a pain in the a**.

 

[sepr2]

Isnt the high gear ratio the same on 3 and 4 speeds? Why more top end?

 

[duneFJ40]

Isnt the high gear ratio the same on 3 and 4 speeds? Why more top end?

I think they are the both. Final drive 1:1. Thanks for the opinions and suggestions. Keep them coming! I'm on the fence.

 

[Roryfj4062]

i did this swap last winter, as i was putting a new to me 2f in, figured i might as well ditch the 3spd at the same time. price seems a little steep, i got my running 2f for $100, and payed $200 for the trans and case. i was also able to get proper length drive shafts from a parts guy in my neck of the woods which made things really easy. just had to mix and match drive shaft pieces with the appropriate flanges. synchronized first gear is a BIG bonus, much easier to slip it into first while rolling. lower first gear was nice for me as i'm running 33" tires with the stock 4.11s. i bolted it all together in the garage, lowered my bezel, and put it all in in one piece. if you're patient, you should be able to find a better deal. you definately won't miss the 3spd.

 

[FF LC FREAK]

I just did the swap as well over the winter. I love how people chime in on price. The market you are in dictates the price you will pay. $350 around here is maybe a little high, but not outrageous. I bought my tranny for $90, but trying to find a transfer case to go with it was a pain. I just kept my 3 speed case and bought the kit from Downey to attach it to a 4 speed. It really wasn't that tough. But by the time I bought the kit and everything to convert my 3 speed case over, I was probably close to $300 for everything.

Overall, I am very pleased with it. Shifting wise, it is much more enjoyable to drive. I have 33" tires, and with the 3 speed, it felt gutless starting out. With the 4 speed, if feels like I have much more power. I can get up to speed much quicker. Definitely worth it, in my opinion.

The one downside is losing the column shifter. I did like that aspect of the 3 speed.

Oh, and there is NO difference in top end. Both have a top gear ratio of 1:1.

 

[texfj40]

Like others said above, top gear is the same in both. I would rather have the 3 speed as is in my original '71. Upside, less shifting, less clutch, 1st gear is low enough, I can idle in first gear and it runs slow like a tractor. If I want it lower (extremely rare), I put it in 4wd low and it will climb up a tree and down the other side. I can ride neighborhood streets in 2nd and put in high gear at 20mph, smooth as silk without labor all the way to highway speed. The only downside, and I see it as a plus is the non-synchro 1st. It keeps me from running stop signs. I like old school.

 

[Dusty 66]

Best upgrade IMHO synchronized first gear for one, 4 speed First gear is lower too more street-able second and third will get you around better and in the sand or mud conditions better without loosing your RPMs as a three speed will leave you trying to stay out of first with no synchro PITA.
better engine brake selection third gear going down steep highway grades.
If you go with the 4 Speed and if you keep you three speed transfer case it gives you a 16% gear reduction in low range too.

 

[Thornton]

I went with changing the 3spd tranny and transfer in my '71 to a '78 4spd and transfer. Like everyone says the syncronized 1st gear is nice. Also like the floor shifter instead of the column, more moving parts to go wrong in column linkage. You still have 1 to 1 in 4th same as 3rd in the 3 spd. You will need to change out the drive shafts, front gets longer back gets shorter. Also the pinion flanges are a different bolt pattern. You can get new ones from SOR that should match your coarse spline pinion and give you both bolt patterns.
What you may want to consider is the 4spd and adapting your 3spd t-case to it. After taking mine on a couple of events this past year the lower gearing would have been nice.
By the way, your also looking at changing out your bellhousing, flywheel, clutch.
Think it out before you jump into. Have fun
ps: price seems steep

 

[Living in the Past]

By the way, your also looking at changing out your bellhousing, flywheel, clutch.

Bell housing has to changed but the flywheel/clutch doesn't need to be changed. You just need to use all matching parts, can't mixed the two parts. I've been running a H42 behind my 68's F engine since 1994 with a three clutch

 

[llih]

For me the money would be better spent on a PS or disc brake swap if it hasn't already been done. I have had my 73 since 1975 and have never needed anything any lower. The 3 speed is paid for, unless it is broke drive the crud out of it. You can always change the shifter location to the floor if that is what your wanting.

 

[duneFJ40]

For me the money would be better spent on a PS or disc brake swap if it hasn't already been done. I have had my 73 since 1975 and have never needed anything any lower. The 3 speed is paid for, unless it is broke drive the crud out of it. You can always change the shifter location to the floor if that is what your wanting.

Good point. I sometimes get carried away when it comes to cars. My shifter is on the floor so that's not an issue. I'm in process of hooking up my winch... That should tide me over for a while.

Thanks

 

[Cruiserdrew]

Look at it this way...

the 4 speed has 4 syncronized forward gears.

The 3 speed has 2 syncronized forward gears.

Big difference in drivability.

If you plan to do any offroading, the lower first gear will be a significant advantage as well.